1. Field of the Invention
A planar transformer for an electrosurgical device to minimize stray capacitance.
2. Description of the Prior Art
A common problem in the field of electro-surgery is the leakage of HF current. This leakage depends in large part on stray capacitance. A significant portion of this stray capacitance is attributable to the output transformer of the electro-surgical device or RF unit. Thus, stray capacitance can be reduced or minimized through the proper design of the transformer.
U.S. Pat. No. 4,255,735 discloses a device for transforming an alternating current-voltage which including a core, a primary winding subassembly and a second winding subassembly. One or both of the primary and second winding subassemblies consists of at least one pair of equal turn and approximately equal resistance windings wrapped co-directionally around the core, each having an equal number of tapped sections. A special tandem switch selectively interconnects tapped sections within winding pairs to provide a desired output terminal winding array such that all sections connected through the switch are energized, and are in the current carrying path at all selected switch positions. The primary and secondary windings are asymmetrically disposed in relation to each other while the leakage reactance is unequal when connected to place less than all of the tapped sections of each in parallel.
U.S. Pat. No. 4,547,721 shows a transformer structure having three cores disposed to define two transformer winding carriers. Each core comprises a pair of C-shaped sections to form pairs of legs joined by connecting portions. A first leg of the first core and a second leg of the second core delimit one of the transformer winding carriers. A third leg of the-second core and a fourth leg of the third core delimit the other transformer winding carriers. The winding includes a primary transformer winding having at least a first coil and a second coil, and a secondary transformer winding having a first and a second coil. The first coils of the primary and second winding are wound along the first transformer winding carrier while the second coils of the primary and secondary transformer windings are wound along the second transformer winding carrier. The primary coils are wound in parallel in such a way that the AC voltage polarity in the two primary coils is 180 degrees out of phase with respect to one another and the AC voltage polarity in the two secondary coils is 180 degrees out of phase with respect to one another.
U.S. Pat. No. 6,154,376 describes reveals a high-frequency, high-density power conversion system providing loss less power switching with a single or double-ended power converter.
U.S. Pat. No. 6,529,389 shows a transformer comprising a primary coil, a secondary coil and a magnetic core. The secondary coil configured to provide a regulated DC output voltage and/or current. The primary coil operates the transformer as a low voltage input converter and as a high voltage input converter.
2002/01545520 teaches a universal switching power supply for generating one or more output voltage levels operable over a range of AC and DC input supply voltages. The universal switching power supply includes an intrinsically safe output, comprising a multi-layer PCB with a planar core transformer.
Additional examples of the prior art are found in U.S. Pat. Nos. 3,299,384 and 4,999,597.